Rachel loves to bake cookies, but she has an old oven that has trouble maintaining a constant temperature. Assume the acceptable temperature range for making the cookies is 350 plus or minus 15 degrees. Six Sigma quality (3.4 defects per million units produced) is probably a bit much to ask of Rachel’s old oven. a. What would the standard deviation in the temperature of her oven need to be if she settled for a "Three Sigma" level of quality? (Round your answer to 2 decimal places.)